In recent years, due to the popularization of cellular phones incorporating camera functions, small-sized imaging units have been developed, which are able to be mounted in various portable electronic devices. Unexamined Japanese Patent Application Publication Number 2006-279,368, discloses an imaging unit which incorporates a zoom lens using an auto focusing method, and an imaging unit which has a camera-shake preventing function. Generally, in said auto focusing imaging unit, a movable lens unit is provided in front of an imaging element having a rectangular imaging area (that is, the movable lens unit is provided on the subject side with respect to the imaging element), and a light-amount controlling devices, such as a shutter and a diaphragm, are provided in front of the movable lens unit. In imaging unit 101 (see FIG. 12) disclosed in above Patent Document, smooth impact drive mechanism 120 (hereinafter referred to as “SIDM 120”) is employed to serve as a driving source of movable lens unit 102. SIDM 120 is a translatory movement actuator, activated by not only rapid volume change of a piezoelectric element, being not illustrated, but also by inertia and friction of moving body 125.
SIDM 120 is structured of: a main body including a holding section (which is not illustrated), a piezoelectric element, and driving shaft 123, connected in said order; and moving body 125 which is connected to driving shaft 123 with friction, wherein moving body 125 supports movable lens unit 102 so that, in imaging unit 101, SIDM 120 is employed as a driving source of the zooming function.
In imaging unit 101, incorporating auto-focusing movable lens unit 102 shown in FIG. 12, movable lens unit 102 tends to slightly rotate around an optical axis for auto-focusing so that captured images tend to become blurred. In order to prevent said blurred image, mounted is rotation regulating mechanism 150 (serving as a rotation regulating section) of movable lens unit 102. Said rotation regulating mechanism 150 is structured of concave section 152, formed on moving body 125 to support movable lens unit 102, and convex section 151 to slidably engage said concave section 152. A small clearance is provided between concave section 152 and convex section 151 so that movable lens unit 102 can move smoothly in the optical axial direction. At the image capturing moment, movable lens unit 102 becomes stationary on the optical axis, whereby said clearance between concave section 152 and convex section 151 does not adversely work on the image capturing operation.
However, if a camera-shake preventing function is to be applied on imaging unit 101, as disclosed in the above Patent Document, an XY-driving section is added, which drives moving body 125 to support movable lens unit 102, in a direction from right to left, and up and down (which are the XY directions), which are perpendicular to the optical axis, whereby moving body 125 may always be moved by said XY-driving sections, in the directions to overcome the camera-shake occurring in the XY directions. Accordingly, even when movable lens unit 102 becomes stationary in the optical axial direction at the image capturing moment, moving body 125 may be vibrated in the XY directions by the XY-driving section. That is, movable lens unit 102 may be vibrated due to micro-motion generated in the small clearance provided between concave section 152 and convex section 151, whereby the camera-shake preventing function cannot exert a greater effect at the image capturing moment, which has been a major problem.